diff --git a/desktop/scripts/build-sidecars.ts b/desktop/scripts/build-sidecars.ts
index 261f25d3..d98597df 100644
--- a/desktop/scripts/build-sidecars.ts
+++ b/desktop/scripts/build-sidecars.ts
@@ -26,21 +26,17 @@ if (scanExit !== 0) {
 
 await mkdir(binariesDir, { recursive: true })
 
+// 单一合并 sidecar：server / cli 共享一份 bun runtime + 共享依赖代码。
+// 调用方（Tauri lib.rs / conversationService）通过第一个 positional 参数
+// 选择 'server' 或 'cli' 模式，详见 desktop/sidecars/claude-sidecar.ts。
 await compileExecutable({
-  entrypoint: path.join(desktopRoot, 'sidecars/server-launcher.ts'),
-  outfileBase: path.join(binariesDir, `claude-server-${targetTriple}`),
-  productName: 'Claude Code Server',
+  entrypoint: path.join(desktopRoot, 'sidecars/claude-sidecar.ts'),
+  outfileBase: path.join(binariesDir, `claude-sidecar-${targetTriple}`),
+  productName: 'Claude Code Sidecar',
   bunTarget,
 })
 
-await compileExecutable({
-  entrypoint: path.join(desktopRoot, 'sidecars/cli-launcher.ts'),
-  outfileBase: path.join(binariesDir, `claude-cli-${targetTriple}`),
-  productName: 'Claude Code CLI',
-  bunTarget,
-})
-
-console.log(`[build-sidecars] Built desktop sidecars for ${targetTriple} (${bunTarget})`)
+console.log(`[build-sidecars] Built desktop sidecar for ${targetTriple} (${bunTarget})`)
 
 async function detectHostTriple() {
   const proc = Bun.spawn(['rustc', '-vV'], {
diff --git a/desktop/sidecars/claude-sidecar.ts b/desktop/sidecars/claude-sidecar.ts
new file mode 100644
index 00000000..363abc67
--- /dev/null
+++ b/desktop/sidecars/claude-sidecar.ts
@@ -0,0 +1,64 @@
+/**
+ * Claude Code 桌面端合并 sidecar 入口。
+ *
+ * 历史上 server 和 cli 是两个独立的 bun-compile 二进制，各自携带一份
+ * ~55MB 的 bun runtime。把两份合并成一个二进制只保留一份 runtime，
+ * 是 P0 之后剩余空间的最大优化点。
+ *
+ * 调用约定（必须由调用方传第一个 positional 参数选择模式）：
+ *
+ *   claude-sidecar server --app-root <path> --host 127.0.0.1 --port 12345
+ *   claude-sidecar cli    --app-root <path> [其它 CLI 参数...]
+ *
+ * 任何模式都必须先做 process.env / process.argv 设置，再 await 进入相应的
+ * 子模块树，原因和 server-launcher.ts / cli-launcher.ts 注释一致 ——
+ * src/server/index.ts 顶层立刻读 process.argv，必须在它求值前 splice 掉
+ * --app-root 和 mode 这些 launcher-only 参数。
+ */
+
+const rawArgs = process.argv.slice(2)
+if (rawArgs.length === 0) {
+  console.error('claude-sidecar: missing mode argument (expected "server" or "cli")')
+  process.exit(2)
+}
+const mode = rawArgs[0]!
+const restArgs = rawArgs.slice(1)
+
+const { appRoot, args } = parseLauncherArgs(restArgs)
+
+process.env.CLAUDE_APP_ROOT = appRoot
+process.env.CALLER_DIR ||= process.cwd()
+process.argv = [process.argv[0]!, process.argv[1]!, ...args]
+
+await import('../../preload.ts')
+
+if (mode === 'server') {
+  const { startServer } = await import('../../src/server/index.ts')
+  startServer()
+} else if (mode === 'cli') {
+  await import('../../src/entrypoints/cli.tsx')
+} else {
+  console.error(`claude-sidecar: unknown mode "${mode}" (expected "server" or "cli")`)
+  process.exit(2)
+}
+
+function parseLauncherArgs(rawArgs: string[]): { appRoot: string; args: string[] } {
+  const nextArgs: string[] = []
+  let appRoot: string | null = process.env.CLAUDE_APP_ROOT ?? null
+
+  for (let index = 0; index < rawArgs.length; index++) {
+    const arg = rawArgs[index]
+    if (arg === '--app-root') {
+      appRoot = rawArgs[index + 1] ?? null
+      index += 1
+      continue
+    }
+    nextArgs.push(arg!)
+  }
+
+  if (!appRoot) {
+    throw new Error('Missing --app-root for claude-sidecar')
+  }
+
+  return { appRoot, args: nextArgs }
+}
diff --git a/desktop/sidecars/cli-launcher.ts b/desktop/sidecars/cli-launcher.ts
deleted file mode 100644
index 06019bb3..00000000
--- a/desktop/sidecars/cli-launcher.ts
+++ /dev/null
@@ -1,38 +0,0 @@
-/**
- * Claude Code 桌面端 CLI sidecar 入口。
- *
- * 与 server-launcher.ts 同理：通过字面量 specifier 的 dynamic import
- * 让 `bun build --compile` 把整棵 src/entrypoints/cli.tsx 依赖图静态
- * 内联进二进制。运行时不再依赖磁盘上的 src/ 或 node_modules/。
- */
-
-const { appRoot, args } = parseLauncherArgs()
-
-process.env.CLAUDE_APP_ROOT = appRoot
-process.env.CALLER_DIR ||= process.cwd()
-process.argv = [process.argv[0]!, process.argv[1]!, ...args]
-
-await import('../../preload.ts')
-await import('../../src/entrypoints/cli.tsx')
-
-function parseLauncherArgs() {
-  const rawArgs = process.argv.slice(2)
-  const nextArgs: string[] = []
-  let appRoot: string | null = process.env.CLAUDE_APP_ROOT ?? null
-
-  for (let index = 0; index < rawArgs.length; index++) {
-    const arg = rawArgs[index]
-    if (arg === '--app-root') {
-      appRoot = rawArgs[index + 1] ?? null
-      index += 1
-      continue
-    }
-    nextArgs.push(arg)
-  }
-
-  if (!appRoot) {
-    throw new Error('Missing --app-root for claude-cli sidecar')
-  }
-
-  return { appRoot, args: nextArgs }
-}
diff --git a/desktop/sidecars/server-launcher.ts b/desktop/sidecars/server-launcher.ts
deleted file mode 100644
index eadf059c..00000000
--- a/desktop/sidecars/server-launcher.ts
+++ /dev/null
@@ -1,44 +0,0 @@
-/**
- * Claude Code 桌面端 server sidecar 入口。
- *
- * 这里把 src/server 这棵树通过字面量 specifier 的 dynamic import 拉进来，
- * `bun build --compile` 会把它们作为静态依赖完整内联进单个二进制 ——
- * 编译后运行时不再需要磁盘上的 src/ 或 node_modules/。
- *
- * 注意：先做 process.env / process.argv 设置，再 await import，这样
- *   - src/server/index.ts 顶层读 process.argv 时拿到的是被剥过 --app-root 的值；
- *   - preload.ts 设置的 MACRO 全局在 server 模块求值前到位。
- */
-
-const { appRoot, args } = parseLauncherArgs()
-
-// 维持 conversationService → CLI 子进程的兼容契约：CLI sidecar 仍然
-// 接受 --app-root 参数，所以 server 这边把它原样透传到环境变量里。
-process.env.CLAUDE_APP_ROOT = appRoot
-process.argv = [process.argv[0]!, process.argv[1]!, ...args]
-
-await import('../../preload.ts')
-const { startServer } = await import('../../src/server/index.ts')
-startServer()
-
-function parseLauncherArgs() {
-  const rawArgs = process.argv.slice(2)
-  const nextArgs: string[] = []
-  let appRoot: string | null = process.env.CLAUDE_APP_ROOT ?? null
-
-  for (let index = 0; index < rawArgs.length; index++) {
-    const arg = rawArgs[index]
-    if (arg === '--app-root') {
-      appRoot = rawArgs[index + 1] ?? null
-      index += 1
-      continue
-    }
-    nextArgs.push(arg)
-  }
-
-  if (!appRoot) {
-    throw new Error('Missing --app-root for claude-server sidecar')
-  }
-
-  return { appRoot, args: nextArgs }
-}
diff --git a/desktop/src-tauri/src/lib.rs b/desktop/src-tauri/src/lib.rs
index aed1b733..da5803c7 100644
--- a/desktop/src-tauri/src/lib.rs
+++ b/desktop/src-tauri/src/lib.rs
@@ -105,11 +105,13 @@ fn start_server_sidecar(app: &AppHandle) -> Result<ServerRuntime, String> {
     let app_root = resolve_app_root(app)?;
     let app_root_arg = app_root.to_string_lossy().to_string();
 
+    // 单一合并 sidecar：第一个参数选 server / cli 模式。
     let sidecar = app
         .shell()
-        .sidecar("claude-server")
-        .map_err(|err| format!("resolve server sidecar: {err}"))?
+        .sidecar("claude-sidecar")
+        .map_err(|err| format!("resolve sidecar: {err}"))?
         .args([
+            "server",
             "--app-root",
             &app_root_arg,
             "--host",
diff --git a/desktop/src-tauri/tauri.conf.json b/desktop/src-tauri/tauri.conf.json
index dfc09528..80c24ddf 100644
--- a/desktop/src-tauri/tauri.conf.json
+++ b/desktop/src-tauri/tauri.conf.json
@@ -44,8 +44,7 @@
     "targets": "all",
     "createUpdaterArtifacts": true,
     "externalBin": [
-      "binaries/claude-server",
-      "binaries/claude-cli"
+      "binaries/claude-sidecar"
     ],
     "resources": {},
     "icon": [
diff --git a/src/server/services/conversationService.ts b/src/server/services/conversationService.ts
index 0fff4098..a7ee07eb 100644
--- a/src/server/services/conversationService.ts
+++ b/src/server/services/conversationService.ts
@@ -448,19 +448,29 @@ export class ConversationService {
   }
 
   private resolveBundledCliPath(): string | null {
+    // 桌面端 P0+P2 之后只有一个合并的 sidecar 二进制 —— `claude-sidecar`，
+    // 它通过第一个 positional 参数 (server / cli) 选模式。当前进程要么
+    // 已经是这个 sidecar 自己（spawn 子 CLI 时复用同一个文件），要么是
+    // 旧 dev 模式下走 bin/claude-haha。这里支持两种命名：
+    //   - 桌面端 prod build：进程名 claude-sidecar*
+    //   - 旧 server-only 二进制（向后兼容）：claude-server*
     const execPath = process.execPath
     const execName = path.basename(execPath)
 
-    if (!execName.startsWith('claude-server')) {
-      return null
+    if (execName.startsWith('claude-sidecar')) {
+      // 复用同一个二进制，调用 cli 模式
+      return execPath
     }
 
-    const bundledCliPath = path.join(
-      path.dirname(execPath),
-      execName.replace(/^claude-server/, 'claude-cli'),
-    )
+    if (execName.startsWith('claude-server')) {
+      const bundledCliPath = path.join(
+        path.dirname(execPath),
+        execName.replace(/^claude-server/, 'claude-cli'),
+      )
+      return fs.existsSync(bundledCliPath) ? bundledCliPath : null
+    }
 
-    return fs.existsSync(bundledCliPath) ? bundledCliPath : null
+    return null
   }
 
   private resolveCliArgs(baseArgs: string[]): string[] {
@@ -473,9 +483,21 @@ export class ConversationService {
       return ['bun', cliCommand, ...baseArgs]
     }
 
+    const cliBaseName = path.basename(cliCommand)
+
+    // 合并 sidecar 模式：第一个参数必须是 'cli'，后面跟 --app-root 透传
+    if (cliBaseName.startsWith('claude-sidecar')) {
+      const args = ['cli', ...baseArgs]
+      if (process.env.CLAUDE_APP_ROOT) {
+        return [cliCommand, 'cli', '--app-root', process.env.CLAUDE_APP_ROOT, ...baseArgs]
+      }
+      return [cliCommand, ...args]
+    }
+
+    // 旧两段式 sidecar：claude-cli 二进制需要 --app-root
     if (
       process.env.CLAUDE_APP_ROOT &&
-      path.basename(cliCommand).startsWith('claude-cli')
+      cliBaseName.startsWith('claude-cli')
     ) {
       return [
         cliCommand,